Optically readable tags encode data in an optically readable format, and allow machine vision systems to identify objects associated with tags. Some optically readable tags, such as bar codes, are considered to be one-dimensional in that the tags encode information in a format that can be read via a scan along one direction. Other tags are considered to be two-dimensional in that the tags encode information along two directions.
Optically readable tags generally comprise regions of highly contrasting optical appearance, such as black and white regions, that represent different values. The use of such optically contrasting regions permits a machine vision system to read a tag more easily compared to tags with less contrast. However, the tag appearance may also detract from the aesthetics of an object that carries the tag.